XML网格无法展开

我有一个父网格(“输出”)托管2个较小的网格。

较小的网格MainDisplay(它基本上在ViewBox中显示一个图像,我想占据除2个子网格中另一个子网格中的300之外的所有水平空间)和Input(固定宽度为300,实际上可以按预期工作)。

我的问题是:

1) 父栅格不会占用所有的水平空间。我想要额外的空间进入ViewBox的网格。

我在屏幕上撒了“HorizontalAlignment=“Stretch”和“Width=“*”,但不会占用所有空间!

2) 我后面有代码来获取图像的宽度/高度。除非我明确设置了高度和宽度,否则后面的代码会试图获取高度和宽度并崩溃。。。但如果我明确设置宽度/高度,恐怕它不会占用可用空间。

这是代码:

<Grid x:Name="Output" Background="#1D1D1D" Margin="0,2,0,-2" HorizontalAlignment="Stretch">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="300"/>
    </Grid.ColumnDefinitions>
    <Grid x:Name="MainDisplay" HorizontalAlignment="Stretch" VerticalAlignment="Top" Grid.Column="0">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Viewbox Width="Auto" Height="Auto" MinWidth="400" MinHeight="400" x:Name="Scenario4ImageContainer" Stretch="Uniform">
            <Image x:Name="Scenario4Image" PointerPressed="Scenario4Image_PointerPressed" HorizontalAlignment="Stretch"  />
        </Viewbox>
    </Grid>
    <Grid Width="300" x:Name="Input" Grid.Column="1">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0">
            <TextBlock Style="{StaticResource BasicTextStyle}" TextWrapping="Wrap" 
                       Text="Tools" />
            <Grid Margin="0,10,0,0">
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="230" />
                    <ColumnDefinition />
                </Grid.ColumnDefinitions>

                <Button Grid.Row="0" Grid.Column="0" HorizontalAlignment="Stretch" Background="DarkSlateGray"
                        Content="Draw Mandelbrot set" Click="DrawMandelbrotSet_Click" />
                <TextBlock x:Name="Scenario4DrawMandelbrotDescription" Grid.Row="0" Grid.Column="1" 
                           Style="{StaticResource BasicTextStyle}" TextWrapping="Wrap" VerticalAlignment="Center"
                           Text="Text." />

                <Button x:Name="Scenario4SetSourceButton" Grid.Row="1" Grid.Column="0" HorizontalAlignment="Stretch"
                        Content="Load image using SetSource" Click="LoadImageUsingSetSource_Click" />
                <TextBlock x:Name="Scenario4SetSourceDescription" Grid.Row="1" Grid.Column="1" 
                           Style="{StaticResource BasicTextStyle}" TextWrapping="Wrap" VerticalAlignment="Center"
                           Text="Text." />

                <Button x:Name="Scenario4LoadImageButton" Grid.Row="2" Grid.Column="0" HorizontalAlignment="Stretch" 
                        Content="Load image using PixelBuffer" Click="LoadImageUsingPixelBuffer_Click" />
                <TextBlock x:Name="Scenario4LoadImageDescription" Grid.Row="2" Grid.Column="1" 
                           Style="{StaticResource BasicTextStyle}" TextWrapping="Wrap" VerticalAlignment="Center"
                           Text="Text." />
            </Grid>
        </StackPanel>
    </Grid>